For many applications and particularly airborne equipment and spacecraft instruments, there is a need for a compact cryogenic cooler capable of reliable operation over an extended period of time. Although there are many such apparatus in existence, they are either subject to wear which requires the servicing and replacement of parts or are extremely complicated and expensive to construct. The Stirling cycle has been successfully employed in many kinds of refrigeration apparatus; however, such apparatus has necessarily included complicated drive mechanisms, rubbing seals and bearings which require lubrication. The complicated drive mechanisms result in increased failure modes while the rubbing seals, bearings and lubricants, in addition to the wear, produce internal contamination which contamination is also aggravated by the use of organic and other outgassing materials within the system.
It is desirable, therefore, to be able to provide a closed cycle machine with moving parts that will reliably run for an extremely long length of time, for example, three to five years, while unattended. To date, no previous approach has been able to provide a long lifetime space-borne cooler system that will reliably run for billions of cycles without failure.